The present invention relates to a bipedal robot.
Bipedal robots which have in recent years been proposed for practical use by the present applicant and others and which have been known in general are basically human-shaped robots. Like human beings, they have two legs extending from a hip at the lower end of an upper body (torso), two arms extending from shoulders on the left and right opposite sides of the upper body, and a head mounted on the upper end of the body and incorporating an imaging device for robot vision.
Some of the robots of the above type are supplied with electric power for operating the legs and arms from an external source through a cable. However, those robots have a limited range of movement, and the handling of the cable is complex. Therefore, it is desirable for robots themselves to carry an electric energy storage device such as a battery or the like as a power supply for operating them.
Electric energy storage devices such as a battery or the like which are mounted on robots as the power supply for operating the robot need to have a relatively large capacity for allowing the robot to move continuously for a sufficient period of time, and hence are relatively large in size and weight. Bipedal robots are essentially more liable to lose attitude stability when subjected to disturbance or the like than robots having many legs.
It has therefore been an important task to study which location and what layout a large and heavy electric energy storage device is to be mounted in on a bipedal robot, for achieving attitude stability when the robot walks and works.
The present invention has been made in view of the above background. It is an object of the present invention to provide a bipedal robot having an electric energy storage device mounting structure which makes it possible to easily achieve attitude stability when the robot walks and works.
In order to achieve the above object, a bipedal robot according to the present invention is available in two aspects. According to the first aspect, a bipedal robot having an electric energy storage device for operating the robot is characterized in that said electric energy storage device is mounted on an upper body of the robot such that the electric energy storage device has a center-of-gravity point present at a position upward of the center-of-gravity point of the robot from which said electric energy storage device is removed and which is in an upstanding state.
It is customary to control the attitude stabilization of a bipedal robot based on an inverted pendulum-type dynamic model as disclosed in Japanese laid-open patent publication No. 5-337849 or U.S. Pat. No. 5,459,659 by the present applicant. The attitude stabilization is controlled by controlling a torque around ankles of the robot with the behavioral characteristics of perturbation of the position of the upper body of the robot being simulated by the behavioral characteristics of an inverted pendulum. A robot under such attitude stabilization control can achieve better robot attitude stability if the center of gravity of the overall robot is in a higher position than it is in a lower position (a vertical position closer to the floor that is contacted by the feet of the robot).
According to the first aspect of the present invention, as described above, the electric energy storage device is mounted on the upper body of the robot such that the electric energy storage device has a center-of-gravity point present at a position upward of the center-of-gravity point of the robot from which said electric energy storage device is removed and which is in an upstanding state. Specifically, the upper body is the torso (body) of the robot from which the legs and arms extend.
With the above arrangement, the center of gravity of the robot including the electric energy storage device is present in a higher vertical position on the robot, thus increasing the stability of the attitude when the robot walks and works.
The first aspect of the present invention is optimum for a bipedal robot whose attitude stabilization is controlled based on an inverted pendulum-type dynamic model, as described above.
According to the second embodiment, a bipedal robot having an electric energy storage device for operating the robot and arms extending from shoulders on an upper body of the robot is characterized in that said electric energy storage device is mounted on the upper body of the robot such that the electric energy storage device has a center-of-gravity point present at a position rearward, in a forward and rearward direction of the robot, of the center-of-gravity point of the robot from which said electric energy storage device is removed and which is in an upstanding state, and the shoulders on the upper body of the robot, to which said arms are coupled, are disposed in a position forward, in the forward and rearward direction of the robot, of the center-of-gravity point of the robot from which said electric energy storage device is removed and which is in the upstanding state.
In the present specification, the forward and rearward direction of the robot means a direction perpendicular to the direction (lateral direction) in which the two legs of the robot are parallel to each other and the vertical direction of the robot when the robot is in the upstanding state.
According to the second aspect of the present invention, since the shoulders on the upper body of the robot, to which the arms of the robot are coupled, are disposed in a position near a frontal surface of the robot, when the arms are extended forwardly of the robot, they can grip an object in a relatively far position forward of the robot. At this time, when the arms of the robot are extended forwardly, the center of gravity of the robot except the electric energy storage device is displaced relatively largely forwardly of the robot. However, the electric energy storage device which is a heavy object is positioned rearwardly of the robot (on the rear surface thereof). Consequently, the center of gravity of the overall robot assembly including the electric energy storage device is not displaced largely forwardly of the robot. As a result, the stability of the attitude of the robot is achieved with ease even when the robot works with the arms extended forwardly. According to the second aspect of the present invention, therefore, it is possible to achieve the stability of the attitude of the robot with ease while the robot is working with the arms at a relatively far position forward of the robot.
According to the second aspect of the present invention, as with the first aspect described above, the electric energy storage device is preferably mounted on the upper body of the robot such that the electric energy storage device has a center-of-gravity point present at a position upward of the center-of-gravity point of the robot from which said electric energy storage device is removed and which is in an upstanding state.
With the above arrangement, the stability of the attitude can be increased when the robot walks and works.
In the second aspect of the present invention, if said robot has an imaging device present upwardly of the upper body of the robot and supported on an upper end of the upper body of the robot, then said imaging device and the upper body of the robot are preferably coupled to each other by a joint disposed in a position forward, in the forward and rearward direction of the robot, of the center-of-gravity point of the robot from which said electric energy storage device is removed and which is in the upstanding state.
With the above arrangement, since the imaging device and the arms are present near the frontal surface of the robot, the imaging device and the arms, and the electric energy storage device on the rear surface of the robot tend to be balanced in weight, making it possible to achieve the stability of the attitude of the robot with greater ease.
According to the first and second aspects of the present invention, an electric energy storage device mounting unit disposed on an upper body of the robot for mounting said electric energy storage device therein preferably has an opening defined in an upper end thereof when the robot is in the upstanding state, said electric energy storage device being insertable into and removable from said electric energy storage device mounting unit through said opening.
With the above arrangement, if the robot is relatively small, then since the electric energy storage device can be inserted into and removed from the electric energy storage device mounting unit through the opening in the upper end thereof, the electric energy storage device can easily be removed and mounted for maintenance or the like. Furthermore, inasmuch as the electric energy storage device can be removed and mounted while the robot is squatting down, it is possible to remove and mount the electric energy storage device while keeping the robot in a stable attitude. As the electric energy storage device mounting unit has the opening in its upper end, even when the robot works at various attitudes, the electric energy storage device is free of the danger of being dislodged from the electric energy storage device mounting unit. Particularly in the first aspect of the present invention in which the electric energy storage device is mounted in a location on an upper portion of the robot, the electric energy storage device is liable to suffer damage if the electric energy storage device falls off due to a failure of a lid over the opening of the electric energy storage device mounting unit. However, the above arrangement is effective to prevent such a shortcoming from occurring.
The electric energy storage device mounting unit has an electric reception terminal disposed on a lower end thereof when the robot is in the upstanding state, for detachable connection to an electric supply terminal of the electric energy storage device as mounted in said electric energy storage device mounting unit.
With the above arrangement, when the electric energy storage device is inserted into the electric energy storage device mounting unit, the electric supply terminal of the electric energy storage device is connected to the electric reception terminal on the upper body of the robot, and both the terminals remain reliably connected to each other under the weight of the electric energy storage device.